SiC has been investigated for use at high temperatures, for example, between 500° C. and 1500° C., but achieving such use has been problematic, as methods for forming SiC/SiC joints were susceptible to cracking at these high temperatures. Diffusion bonding is one method used for joining SiC to SiC, and such bonding has been achieved using refractory metals foils such as niobium, titanium, molybdenum, nickel, and tungsten, by the formation of carbide and silicide compounds that produce strong bonding and can survive exposures to high temperature. The problem associated with forming a diffusion bond with SiC using metals such as niobium, titanium, molybdenum, nickel, and tungsten is that these metals are converted into carbide and silicide phases in the joint, which are brittle and susceptible to cracking. The formation of cracks means that a hermetic seal cannot be formed using these processes, and the formation of cracks can reduce the strength of the joints. Additionally, the silicide and carbide phases formed in the joint also typically have different physical properties (coefficient of thermal expansion (CTE), elastic modulus, thermal conductivity, etc.) than the SiC base materials, which can produce stresses during thermal cycling that can lead to cracking in the bond region or the SiC adjacent to the joint.
Other attempts to form a SiC bond with a hermetic seal included a brazing composition of approximately 40 to 97% silicon with the rest selected from the group consisting of chromium, rhenium, vanadium, ruthenium, iridium, rhodium, palladium, cobalt, platinum, cerium, and zirconium with some SiC and/or carbon mixed into the material used to form the bond. Other methods differ because they rely upon the formation of molten silicon with various reinforcement phases (one of which may contain iridium) that are formed in the joint. Still other methods were tried, such as polymer infiltration and reaction forming. These other methods are more complicated than diffusion bonding, require 8 to 14 days of processing time, typically contained free silicon that may be detrimental during irradiation, and are generally non-hermetic. Thus, a need exists for a method of diffusion bonding SiC to form a hermetic seal.